1. Field of the Invention
The invention relates to radio frequency identification (RFID) technology, and in particular, to improved RFID readers.
2. Background Art
Radio frequency identification (RFID) tags are electronic devices that may be affixed to items whose presence is to be detected and/or monitored. The presence of an RFID tag, and therefore the presence of the item to which the tag is affixed, may be checked and monitored wirelessly by devices known as “readers.” Readers typically have one or more antennas transmitting radio frequency signals to which tags respond. Because the reader “interrogates” RFID tags, and receives signals back from the tags in response to the interrogation, the reader is sometimes termed as “reader interrogator” or simply “interrogator.”
With the maturation of RFID technology, efficient communication between tags and interrogators has become a key enabler in supply chain management, especially in manufacturing, shipping, and retail industries, as well as in building security installations, healthcare facilities, libraries, airports, warehouses etc.
Current RFID systems suffer from various problems. For example, RFID readers suffer from high costs associated with programmable frequency synthesizers, power amplifiers, and high-speed high-resolution digitizers. However, these and other similar electronic devices are necessary to meet governmental regulatory requirements, such as FCC part 15.247, when designing high performance RFID systems.
Furthermore, if two or more tags and their associated boxes are present within the interrogation space, readers have difficulty distinguishing one tag from another within that interrogation space. For example, if two boxes and their associated tags were present, the interrogator would read the presence of both tags, but specifically determining which box was which is difficult unless one of the boxes is removed to be singulated.
Mobile readers have disadvantages. Readers require relatively large amounts of power to operate, which tends to limit battery life of mobile RFID terminals. Furthermore, readers produce excessive heat when housed in confined spaces such as mobile terminals. Still further, mobile RFID systems require large, bulky antennas to perform far field reads, to enable interrogation at long ranges.
RFID readers and tags are normally very susceptible to interference from other RFID readers in the general area. For example, reader transmissions normally interfere with other readers in the nearby general area. Readers transmitting at full power can even adversely affect the host system by which they are controlled and in which they are housed. When writing to RFID tags, the need for an interference free environment is paramount. Often this requires interference free zones to be configured, so that tags in the interference free zones can be reliably written.
Thus, what is needed are ways to improve a quality of communications between readers and tags in an RFID communications environment.